British police have arrested a nurse on suspicion of murdering three patients by intentionally giving them a saline solution contaminated with insulin.

The nurse, identified as 27-year-old Rebecca Leighton, was arrested after authorities said 14 patients at Stepping Hill Hospital in Stockport were given the contaminated solution. Greater Manchester Police have the woman in custody for questioning and crime scene investigators are searching her apartment.

The contamination was discovered last week when a higher-than-normal number of patients showed unexplained low blood sugar levels. A 44-year-old woman and two men, aged 71 and 84, are believed to have died after receiving the contaminated saline. Another patient is in critical condition, while 10 others are expected to recover.

Hospital officials says security at the hospital has been increased since the suspicious deaths, with the staff ordered to work together in pairs. Sky News reported that all drugs are being double-checked and security guards are monitoring access to medicines.